About to re-render outside of house. Insulation choices pls.

[Udhi]

Hi all,
Due to the state of disrepair, all the outside rendering on my parent's semi had been taken off in preparation for rerendering.

I was thinking of seizing the opportunity and installing some kind of thermal insulation before applying a smooth render on the building.

Can someone suggest solutions please>

I hear the thermal insulation can be applied by way of "thermal plates" oe PIR boards which are screwed onto the brickwork and then smooth render applied over the top.

The second method seems to be some kind of "mixture" which is mixed into the render before application.

 

[regsmyth]

If the house has a cavity, it would probably be best to get this insulated and then re-render as normal.
If not, you could use a system where polystyrene is stuck onto the walls, then a mesh scrim is pasted on, finally a top coat of a hard thin resin, looks like render.
Obviously can create a few difficulties around windows/cills/roof/eaves, but good insulation and apparently will never crack....

 

[ajrobb]

A bit more information would be useful.

• when was it built?
  does it have cavity walls?
  hip roof or gable end?

If there is any doubt about the DPC, external insulation could trap damp in the wall. You have to treat the inside of the external walls to ensure there is a continuous VPL near the warm side from sub-floor to loft or you can cause condensation problems. If there is a vented cavity, external insulation could get bypassed. You should at least ask local planning control if they would need to give planning permission to change the exterior.

 

[Udhi]

Hello,
Thanks for the replies. I have heard of the methods described by regsmyth. This was the main idea until I heard that something could be mixed INTO the render itself for a similar effect.

ajrobb, It is a fairly old deed, possibly very early 1900 or 1855, original farmhouse from where an estate sprang. But the outer walls are cavitied as I remember cavity insulation being injected about 10 years ago. It is double glazed.

There is no damp reported.
GABLE END - yes, on both sides (North & East), it is DETACHED. The eastern end has a garage over which a thermalite room had been beuilt to make it 4 bedroom. Yes, I am aware thermalite is a stupid idea, but it was the past owners idea. This room has a flat roof, leaving another 6 -8 foot gable end.

Thats all I can tell you, I think.

I could promote a full internal Kingspan lining for all external walls like at my house, but I think it would be too disruptive for an established house of nearly 30 years.

 

[mointainwalker]

I don't know if it exists in the UK, but in Germany and France there is a small take -up of render ( or mud or clay ) mixed with either hemp-fibres or different types of straw.

People using these methods normally do it for ecological reasons because it is likely to be much more expensive as so little used.

In most cases it will also be used on a new-build designed for it and not as a treatment on an existing , conventional building.

I honestly would not try it as you are likely to invest a lot of time investigating it , only to finally reject it.

 

[Udhi]

Ok, I agree that REAL natural materials will not be useful here. The house looks new. Its internal plaster does reveal horsehair matrix plaster but the outside was DEFINITELY concrete render.

The render does not come all the way to the ground BTW, it started about 4' from the ground. I think mom wants it smooth rather than the original rough render.

Regards

 

[freddiemercurystwin]

This comes up fairly regularly on here
//www.diynot.com/forums/viewtopic.php?t=198310
//www.diynot.com/forums/viewtopic.php?p=1535129
//www.diynot.com/forums/viewtopic.php?p=1443942#1443942